

function jia(){
   var tex=document.getElementById("leftUnder-num-input");
var a=tex.value; 
a++
tex.value=a
}
function jian(){
    var tex=document.getElementById("leftUnder-num-input");
 var b=tex.value; 
 b--
 if(b<=1){
    tex.value=1
 }else{
    tex.value=b
 }
 }

